<!DOCTYPE html>
<html lang="en"  xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <span th:if="${age>=15}">我满了15岁</span>
    <span th:unless="${age>=15}">我没满了15岁</span>
</body>
</html>